Visual Evoked Potentials in Guinea Pigs with Brain Lesion

Abstract

Visual evoked potentials (VEPs) were recorded in 10 adult male guinea pigs with brain lesion. Lesions were produced in 5 animals by superficial suction of the occipital lobe. The other 5 animals were orally administered with hexachlorophene (about 35 mg/kg/day) for 28 days. In the VEP following the ablation of the occipital lobe, the peaks P₁₀, N₂₀, P₅₅, N₇₅, N₁₄₀ and P₂₀₀ disappeared in many cases. The amplitude of the peak N₄₀ decreased to approximately one half its control VEP. In the VEP obtained from the animals administered with hexachlorophene, the peak latencies of N₂₀, P₃₀, P₅₅, N₇₅ and P₁₀₀ were slightly prolonged after the 7th day following the first administration. On the other hand, there was no change in the latency of N₄₀ during the whole period of administration. The peak-to-peak amplitude showed some variability in different peaks. Histologically, diffuse status spongiosis were found in the white matter of the cerebrum, cerebellum, and brain stem. As described above, the ablation of the occipitallobe caused markedly depressed VEPs, however, the responses to the photic stimulation persisted after the injury. On the other hand, the VEPs of animals administered with hexachlorophene showed a high probability of peak appearance, and a decrease in amplitude was not marked.